Impact of the geometry of divergent chimneys on the power output of a solar chimney power plant

Divergent chimney is proposed to be an alternative for Solar Chimney Power Plants (SCPPs) because of their reported remarkable improvement in power output over cylindrical chimneys. However, the power output of divergent SCPPs in those studies changed from several percentage to >100 times higher than that of cylindrical ones. In our hypothesis, this large deviation was related to the various configurations of the SCPPs examined. Therefore, this paper examined comprehensively the effect of geometry of divergent chimneys on system performance of SCPPs to further reveal their hydrodynamic features. The geometric parameters under investigation included the area ratio (AR) of chimney exit over entrance, the divergent angle (DA) of chimney wall and the size of system. Our numerical simulations indicated a parabolic tendency in the performance of the divergent SCPPs when increasing the ARs (or DAs). Reasons for this tendency were proposed based on its hydro- and thermo-interaction. Furthermore, the normalized power output showed good consistency among the SCPPs with different sizes when geometric similarity was adopted to the entire system geometry. The similar normalized outputs found were almost insensitive to the variations in the solar insolation. These outcomes would be a valuable reference for designing SCPPs with divergent chimneys.